MongoDB connection error: Error: slash in host identifier

[amoungui]

Hello, I'm developing a node.js project with mongodb, express, but I get this error when I start the server:

MongoDB connection error: Error: slash in host identifier
[nodemon] app crashed - waiting for file changes before starting ...

this is my files:
mongoose.js file:

const { mongo, env } = require('./vars');

// set mongoose Promise to Bluebird
mongoose.Promise = Promise;

// Exit application on error
mongoose.connection.on('error', (err) => {
  console.error(`MongoDB connection error: ${err}`);
  process.exit(-1);
});

// print mongoose logs in dev env
if (env === 'development') {
  mongoose.set('debug', true);
}

/**
* Connect to mongo db
*
* @returns {object} Mongoose connection
* @public
*/
exports.connect = () => {
  mongoose.connect(mongo.uri, {
    keepAlive: 1,
    useMongoClient: true,
  });
  return mongoose.connection;
};

my var.js file:

const path = require('path');

// import .env variables
require('dotenv-safe').load({
  path: path.join(__dirname, '../../.env'),
  sample: path.join(__dirname, '../../.env.example'),
});

module.exports = {
  env: process.env.NODE_ENV,
  port: process.env.PORT,
  jwtSecret: process.env.JWT_SECRET,
  jwtExpirationInterval: process.env.JWT_EXPIRATION_MINUTES,
  masterAccount: process.env.MASTER_ACCOUNT_NUMBER,
  masterAccountPassword: process.env.MASTER_ACCOUNT_PASSWORD,
  mongo: {
    uri: process.env.NODE_ENV === 'test'
      ? process.env.MONGO_URI_TESTS
      : process.env.MONGO_URI,
  },
  logs: process.env.NODE_ENV === 'production' ? 'combined' : 'dev',
};

the index.js file:

Promise = require('bluebird'); // eslint-disable-line no-global-assign
const { port, env } = require('./config/vars');
const app = require('./config/express');
const mongoose = require('./config/mongoose');

// open mongoose connection
mongoose.connect();

// listen to requests
app.listen(port, () => console.info(`server started on port ${port} (${env})`));

/**
* Exports express
* @public
*/
module.exports = app;

thanks for you help